The islamic prayer, called solat, is a formal way of worshipping God. The prayer is performed 5 times a day, each at specified period.
Instead of using the bell, drum or gong, the Muslims use the human voice to announce the point of entry of the prayer call, called azan, is made in Arabic throughout the world as thought by Prophet Muhammad.
God says: "Oh, you who believe! When the call is made for prayer...hasten to the rememberance of God." (62:9)
A Muslim begins his prayer in anytime after the entry point of the period and not before it. Hence, to hear the azan is essential. Nowadays, however, copies of the prayer time-table are available and if one does not hear the azan one can refer to the time-table to ascertain the time for one's prayer. The azan is particularly essential if one wants to perform one's prayer in the mosque in congregation because the congregational prayer begins just after a few minutes of the call of the azan. (However, a Muslim who reaches the mosque late can still perform his prayer by joining the congregation at any point during the prayer, and then finishing whichever part he has missed. If the congregational prayer is over when he arrives, he can still perform his prayer individually.)
The azan, in a way, is Islam's international anthem. Anywhere in the world, whether in Britain, Canada, China, India, Indonesia, Morocco or Singapore, the azan is made in exactly the same words as used and tought by the Prophet. This uniformity gives Muslims of any race, colour or culture the sense of belonging, brotherhood and unity in their belief and worship of the One God.
The person who calls out the azan from the mosque is the muezzin. The first person is Islam to be given the honour of calling out the azan was not an Arab but a Negro, a freed slave, named Bilal. Any Muslim can be the muezzin.
(Adapted from "The Splendours of Islam", Darul Arqam Singapore)